Clones on SSD

Just a piece of recent experience I’d like to pass on:

Recently the SMART tests of the G-Tech HD I’ve been using for years for my bootable SuperDuper clones began to forewarn problems, so I got a SanDisk Extreme Portable SSD, which connects to my new MB Air via USB-C. I discovered that not only are the clones now copied faster, but booting from the clone, which took minutes from the HD, is now almost as fast as from the Mac’s own SSD. (I’m just a Mac user, in no way affiliated with SanDisk.)


Spot on! A bootable duplicate has to be fast enough to be usable. I encountered this in:

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After putting duplicates onto SSDs, there’s no way I’m going back to spinning HDs. I’ve been running Big Sur betas from an SSD and don’t notice any performance difference.

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This isn’t surprising. USB 3 (especially the 10G variation) and Thunderbolt are very fast interfaces, so an SSD attached externally will be nearly (if not exactly) as fast as an internal SSD.

The only practical problem with using SSDs for clones and backups is the cost.

FWIW, I’m going to be buying new backup media this weekend and I will be using hard drives. I plan on spending about $400 for three external 4TB hard drives (about $120 per drive, plus $20 per enclosure). One for Time Machine and two for cloning the system (2TB internal storage, plus lots of headroom for CCC’s safety net of older file revisions).

That same capacity in SSD form would cost 4-5 times as much ($500-600 for each drive, plus enclosures). Since I doubt I’ll actually need to boot from a clone, I’m not overly concerned about the speed. Most likely, should I need to boot from it, I will do so just long enough for wipe the computer’s internal storage and clone the system back to it from the external drive (or clone to a new computer or an external SSD if the computer’s internal storage failed).

Make sure you aren’t buying SMR drives or at least that you know you are and are ok with it.

Thanks for the reminder. Since I will be buying from a physical store, I’ll do a web search against specific models to make sure.

I don’t think SMR will matter in my case (aside from the initial backup), but it is still something I’d rather avoid.

Of course, I don’t know what your needs are, so I’m just punting here. To begin with, I’ve been using computers (Apple, then Macs) since 1984. Over all those years, I’ve only absolutely needed to boot from the clone twice, each time to repopulate a Mac which had become hopelessly corrupted (the last time was several years ago). On those two occasions, however, the clone saved my digital life.

You seem to have 2TB or less stored on your computer. I wonder if you always need to have all that stuff instantly at your fingertips all the time. My current MB Air has 512GB storage, more than enough for my usual daily work and needs. But I’ve gots heaps of other, mostly older stuff - old patient records, lectures, literature, some video and such - I might need now and then, or simply don’t want to throw away. For this, my backup drive has a large “Archives” partition next to the smaller volume for the bootable clone, and when I feel something is no longer needed on my Mac I throw it into there. (Archives isn’t backed up, so I know I could possibly lose it, but if it had vitally important stuff I could back that up to another drive, too.) And I also have a Time Machine (not 100% reliable, BTW).

So I can imagine you might want to have one quickly-bootable clone on an external SSD, and use HDs for your Time Machine (which, BTW, might be able to work with SSDs soon) and for backing up what might be your equivalent of Archives. But, as you say, if quick booting from a clone is not a priority, my suggestion is superfluous.

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I see @Shamino’s point, but I have to admit I’m going the other way. I have just grown tired of spinning platters. My early New Year’s resolution is to buy SSDs from here on out. They are clearly more expensive. A 2 GB SSD will set me back $190 (SATA for use over USB3.1 gen 2, PCIe-based over TB3 would obviously be more expensive) while I can get a WD Green for about one third of that. But I just can’t stand slow disks anymore now that I’ve become so used to fast internal disks everywhere. The noise, the bulk, ugh. :no_entry:

So I plan on making a start with new TM disks that I need to be buy soon (for Big Sur), as I detailed in this thread already. I’m also going to be buying two smaller SSDs to use as bootable clones (in two different locations). They can be smaller since I don’t do incremental/preserving clones. I use other backup methods (TM, rsync, remote to work cloud) for that. The clone is really just insurance before I install more significant updates. And long-term storage is another topic entirely (where I still see HDDs as an inexpensive and convenient to tape).

I’ll clearly be spending more money this way, but I’ll also be enjoying good performance and peace of mind. And these days, what else am I going to be spending that money on? Our famous Chez Panisse restaurant hasn’t been doing any dine-in since March and flying to Tahiti isn’t likely going to be an option for another year or so. :laughing:

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OT, but at least you still have Chez Panisse’s Sunday marketplace. And, like us, you’re probably learning to cook better at home :sunglasses:

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The entire computer has 2TB of storage. I’m using about 1TB now, including home directories and documents from two other family members.

I don’t plan to ever actually do work while booted from the clone. It exists so I can quickly restore the entire system in the case of a catastrophic failure (much like how I used to use tape before storage requirements grew too large for an affordable tape drive). As such, I want the clone to hold all of the files. If I need to perform a multi-step restore (restore the OS, then apps, then documents, etc.) then a half-day unattended operation will end up taking several days and require manual intervention throughout the process.

WRT SMR drives, @raleighthings, I did a lot of research this morning after reading your comment. Searching for CMR/SMR reveals only a lot of outdated articles from earlier this year and broad hand-waving statements from manufacturers.

Going directly to the manufacturer web sites and pulling data sheets, on the other hand, worked pretty well. Without presenting all the ugly details (which will make this comment far too large), here’s some useful information:

  • Seagate
    • Barracuda: Unacceptable. Almost all SMR. Only rated for 2400 hours on-time per year (thats 6 hours per day)
    • Barracuda Pro: All CMR, 24x7 operation
    • Iron Wolf and IronWolf Pro: All CMR, 24x7 operation
    • Skyhawk: Mostly CMR, some SMR models, 24x7 operation
    • Skyhawk AI: All CMR, 24x7 operation, very high MTBF numbers
  • Toshiba
    • All but their 2TB laptop drive are CMR
    • The S300 (surveilance), V300 (video) and N300 (NAS) models are rated for 24x7 operation. The other models (X300 (gaming), P300 (PC desktop) and L300 (laptop)) are not.
  • Western Digital
    • Blue: Some models are CMR, some are SMR. No mention about 24x7 operation, which probably means “no”.
    • Black: All CMR. No mention about 24x7 operation
    • Red: All SMR. Rated for 24x7 operation
    • Red Plus: All CMR. 24x7 operation
    • Red Pro: All CMR, 24x7 operation
    • Purple: No mention about SMR/CMR. 24x7 operation
    • I didn’t look at the Enterprise drives, because there were a lot of different series and none are available locally to me.

Unfortunately, Western Digital uses different part numbers on their drives (which the datasheets use) and the retail box. So it’s impossible to look at a retailer’s web site and compare the listed product to a datasheet. Which means Blue drives are out of the running, since I’m not going to support a “you have to buy it to know what it is” mentality.

Combining the above with local availability, my choices for a 4TB, CMR 7200 RPM drive rated for 24x7 operation are narrowed down to:

  • Toshiba N300 ($110)
  • Seagate SkyHawk ($110)
  • WD Red Pro ($145)

Any recommendations? I’m thinking that the Toshiba N300 is probably my best choice here.

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At work they always issue us WD Red Pro for this kind of purpose. In fact, I have two in my office right now. I’ve seen very solid performance from them, nothing to complain about. No excessive noise or heat. I couldn’t say though if that is worth the extra $35. I’ve always been a bit of a WD guy myself so I’ll certainly admit to possible bias here.

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Summary: Fast OWC SSD as boot drive on 2017 iMac is much faster than the built in Fusion drive. Not cheap, but cheaper than a new SSD iMac and similar in price to upgrading the Fusion drive to SSD.

I use a SanDisk 2TB USB-C as a backup for my photos and so I can access the photos while traveling with my 512GB MBP using an adaptor to USB-A—kept current connected to iMac (no travel now). I got tired of the slow Fusion Drive on my 2017 iMac so tried the SanDisk as a boot drive, not a whole lot faster, so I got an OWC 2TB faster SSD and it’s noticeably faster, so it’s my current boot drive with the Fusion drive as a back-up (currently just as it was a few months ago); I have other backups and will leave it as a Catalina boot drive for probably six months after installing Big Sur and then maybe have it as some kind of clone or backup. The SSD has only become unplugged once.

I still use spinning drives for other backups.

My 2¢.

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I totally agree. We’ve still got 2 old spinning disk drives among the SSDs we use for backup, and the speed and noise makes quite a difference. We’ll also be replacing them soon.

SMR spinning rust HDD’s are only a problem when used in RAID solutions. As a standalone drive they are perfectly fine. SMR is less expensive to manufacture and you have to be careful not to use SMR drives in RAID (Redundant Array of Inexpensive Disks).

RAID means multiple HDD’s are used to improve performance, increase storage capacity and offer some redundancy. RAID does NOT equal Backup. Backing up data somewhere else besides a single RAID solution is recommended. Sync data to a second RAID solution or copy important data to cloud, backup, etc.

It’s a problem whenever you will be writing data over an extended period of time. This will frequently be the case for RAID systems (atlhough WD claims it won’t be for small personal RAIDs - an assertion I question.)

But it also will be an issue for making backups. For instance, my initial Time Machine backup wrote 900GB to the new drive. It took about 3 hours to complete (an average of 83 MB/s for three hours). SMR would definitely slow this down.

On the other hand, after the initial backup, subsequent backups (which rarely writes more than 1GB, usually less) probably wouldn’t be affected much.

RAID is an especially nasty case, where the performance problems may result in the RAID software declaring the drive dead, removing it from the array, but a slow-performing drive in other circumstances can still be unacceptable even if it’s not a total catastrophe.

IMO, SMR is not appropriate for any situation that is expected to involve extended periods of write operations. Off the top of my head, this includes:

  • A volume containing swap files/partitions
  • An active transaction database (typically a server application)
  • Video/audio capture and editing
  • Backup devices (especially non-incremental backups where you may be writing hundreds of gigabytes in a single session)

I think there are plenty of applications where large writes happen infrequently (if at all), and SMR shouldn’t be a problem there. But in many cases, you don’t really know (at the time of purchase) what use-cases you will encounter over the life of the drive.

Furthermore, the difference in price isn’t very great. My most recent shopping run showed a difference of $15-25 for a 4TB drive (Seagate Barracuda vs. a Seagate IronWolf, Toshiba X300 or Toshiba N300). And those drives differ in more ways than just SMR-vs-CMR (e.g. the IronWolf and N300 are rated for 24x7 operation vs 8x5. The two Toshiba models are 7200 RPM vs 5400/5900 RPM for the two Seagate models).

In my particular case, since I was explicitly looking for a 7200 RPM drive rated for 24x7 operation, that ended up (coincidentally?) eliminating all of the SMR drives from consideration anyway, so the question ended up being moot for my specific situation.

Well said. ZFS asynchronous writes are an even bigger problem with SMR HDD’s than other hardware / software RAID solutions.

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This is good to know. I love Super Duper, but finding compatible (i.e. bootable) drives has been a challenge over the years. I’m running El Capitan on a mid 2012 Macbook Pro. Is there any reason this drive wouldn’t be compatible with that?

Which drive?

FWIW, I ended up buying three 4TB Toshiba N300 drives and installed them in Vantec NexStar TX enclosures.

I clocked backup speeds at about 166 MB/s using Carbon Copy Cloner to an APFS-formatted volume and a much slower 95 MB/s to make an initial Time Machine backup to an HFS+ volume. (The drive’s documented maximum speed is 204 MB/s).

The clones are bootable. After using the Startup Utility to enable booting from external drives and older macOS releases, I successfully booted and logged in to the clone. Definitely slower than the Mac’s internal SSD and the drive thrashes a lot, but the system was (IMO) still usable. Definitely good enough for the short-term needs to be able to wipe the Mac’s internal file system and clone everything back to it or clone everything to a replacement computer.

Ah, sorry, I was referring to the SanDisk drive mentioned by the original poster.

A separate, but related topic. What are people’s thoughts regarding drive size and number of drives?

Right now I have a 1TB drive partitioned into two. I back up every day, swapping back and forth between the partitions. It’s cheaper and neater to have a single large drive than two 500 GB drives.

But am I tempting fate with that setup? Is it time to go with multiple drives?